Research on distribution, movement and accumulation of marine debris using satellite data

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We collected drifting buoy data and compared ocean surface flow fields derived from the buoy data with those derived from satellite data in order to confirm accuracy of satellite-derived ocean surface flow. We used drifting buoy without a drogue in the present study because we are interested in only surface flow. Basic flow patterns are consistent with each other. However, the values derived from satellite-derived data are extremely low compared with buoy-derived data. Because satellite date are considerably smoothed and a drifting buoy generally tends to concentrate in a strong current region. There are large differences between each flow field in the southern hemisphere compared with the northern hernisphere. The large difference may be caused by low density of drifting data in the southern hernisphere. Moreover, we investigated movement of marine debris discharged from big cities in the world. There are two ways of the movement of the marine debris discharged from Japan. Most marine debris move eastward by the Kuroshio, Kuroshio Extension and North Pacific Current. Parts of marine debris move southwestward by the Kuroshio Countercurrent. Moreover, we investigated an effectiveness of data assimilation for prediction for location of marine debris. The objective analysis method used in the data assimilation method is a successive correction method. We can predict buoy location after one month within 300 km if we use data assimilation. However, the prediction results strongly depend on the density of buoy data.